Monday, April 23, 2012
Solution by Tony Leukering
A flock of ducks winging by often presents little time to adequately assess the species makeup involved... unless you get pictures. With our birds frozen in time, we have quite a bit of time (nearly a week) to ogle the picture and ponder the possibilities.
As noted by all respondents, American Wigeon provides the anchor to our eight-bird flock, with four easily-noted males with their "baldpate" head patterns. When American Wigeon are present, it is always a good idea to check for Eurasian Wigeon, even among the females. As our quiz picture was taken from beneath flying birds, we have an excellent opportunity to be sure whether that Old World species is represented or not, as axillar color is an excellent field mark. Looking at the definite male American Wigeons, we can see white in the axillar region of three of them (the other has one wing in a wrong position to assess the character and the other underwing shaded to obscure it). Eurasian Wigeons sport non-contrasting gray axillars. The top-left bird has contrasting white axillars and a gray-brown head, so that one is a female American Wigeon. The individual duck that is mostly hidden has the slightly-longer central rectrices typical of female wigeons (rather than the somewhat-more-elongated central rectrices of male wigeons). It also has the mottled brown flanks of a female, unlike the smooth pinkish-brown flank of male American Wigeon. Finally, it sports the bright white axillars of an American Wigeon, so a second female American. The top-right bird has a typical female wigeon tail, but the head and chest are concolorous (and brown) and the wings lack any bright white underneath. Our careful analysis of the flock has been rewarded: a female-plumaged Eurasian Wigeon!
At this point, we might discontinue our analysis, as we've found our rarity. But, as noted many times in this venue, when looking at a flock of birds, it is always a good idea to attempt identification of every individual. Yes, we've already found a "good" bird, but that does not mean that there are not two good birds; or even three. I used this picture because it had what I considered the obvious different bird, but also included one that I thought might be overlooked once the odd bird out had been found. Indeed, for this quiz picture, it was true; I just had things backward as to which was the obvious odd duck out. The bottom bird has yellowish (perhaps, with an orange tinge) legs, immediately ruling out any wigeon and leaving us with darned few choices. Mallards have orange legs, so that option should be eliminated by that feature, alone. I understand, however, that color-tone perception is not everyone's skill, particularly males, who seem more prone to various forms of color blindness. But, we do not have to rely on leg color for this ID, for at least a couple of reasons. The tail does not look white, though it is in shadow and we may not be able to discern its true color -- it is paler than the undertail coverts, though. However, we can look at the bird's wing linings and note that the leading edges are dusky, as are the greater secondary coverts and the primary coverts; Mallards sport gleaming white wing linings. With the orange on the bill, we have just one option, Gadwall. But, as noted by one alert respondent, the bird has an apparent black undertail covert region, which would be anomalous for a female Gadwall and male Gadwalls don't have black bills. At least, they don't once they reach adulthood. This bird is probably an immature male that has molted in a black vent, but whose bill has not yet changed from its juvenile color and pattern (this could also explain the apparently palish tail, as immature ducks tails wear and bleach fairly rapidly). I took this picture of six American Wigeon, one Eurasian Wigeon, and one Gadwall from the hawkwatch platform at Cape May Point S. P., Cape May Co., NJ, on 9 November 2011.
Six respondents got no species incorrect, but provided answers with too few species, usually missing the Eurasian Wigeon.
Incorrect species provided as answers:
Mallard - 5
Green-winged Teal - 1
Congratulations to the 13 of 24 respondents getting the quiz correct:
Answer: American Wigeon, Eurasian Wigeon, Gadwall